In order to determine whether aspirin or salicylic acid is present in tissue when it is not measurable in plasma, 15 human subjects will take 640mg of aspirin daily for 14 days. 24 hours after the 14th dose, 10 sigmoid colonic biopsies will be obtained and assayed for aspirin and salicylic acid. To date, no aspirin or salicylic acid were detected in 5 human subjects.